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(11) | EP 1 021 984 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Automatic optometer evaluation method using data over a wide range focusing positions |
| (57) A method and apparatus for measuring refractive properties of a refractive optical
system by fitting measurement data points to a derived function are disclosed. In
a preferred embodiment relating to an automatic objective optometer, each data point
represents a peak signal amplitude extracted from a scan of a plurality of pixels
on an area detector array receiving light from the illuminated refractive optical
system at a particular optometer position. The derived function describes a relationship
between the peak pixel signal and optometer position based on changing focusing conditions
of light at the detector array, which correspond to focusing conditions at an image
plane of the refractive optical system under a confocal arrangement. A first derived
function is applied for fast and slow sphere optometer sweeps through broad and refined
ranges and includes a pair of poles at first and second astigmatic focal points to
give the magnitude of sphere and cylinder powers of the eye, and a second derived
function is applied for a cylinder sweep varying the axis of a non-zero cylinder component
introduced to the illuminating light and includes a single pole for giving the cylinder
axis. |